Antennas are configured to transmit and receive radiation beams having particular, desired patterns. Generally, antennas are reciprocal in that they exhibit similar properties in both transmission and reception modes of operation. As such, while descriptions of antenna performance are often expressed in terms of either transmission or reception, the capability to operate comparably in either mode is understood. In this regard, the terms “aperture illumination,” “beam” and “radiation pattern” may pertain to either a transmission or reception mode of operation. Relatedly, the same antenna “feed” may be employed for both the transmission and reception of signals.
As noted, different antenna configurations are used for different applications. For example, reflector antennas may be used for providing high gain in radar and communications applications. Of particular interest, various reflector antennas utilize a parabolic reflecting surface. Waves arriving at a parabolic reflecting surface in phase are reflected to a focal point along equi-distant paths, thereby arriving at the focal point in phase. Waves leaving a feed located at a focal point reflect off of a parabolic surface to result in a planar wavefront collimated along a focal axis, thereby producing a narrow beam of directed, focused energy.
Various antennas with parabolic reflecting surfaces have been proposed for spaceborne applications, including antennas having paraboloidal reflectors. In the later regard, while an increased diameter of a paraboloidal reflector can increase its gain and efficiency, the desire to limit the size and weight of spaceborne antenna platforms presents a challenging trade-off. Further, the placement of feed componentry can compromise pattern coverage, particularly where wide-angle coverage is desired. Additionally, feed componentry placement in spaceborne applications raises attendant concerns in relation to environmental exposure and outboard mass.